Recently, according to the rapid development of the electronic industry and communication industry, such as various information and telecommunications technologies including mobile communications technology and the demand for light, thin, short and small electronic equipment, mobile IT products, such as notebook PCs, PDAs, digital cameras, and camcorders, have been widely adopted, and thus small sized lithium ion batteries exhibiting high performance, high capacity and high density have been competitively developed all over the world.
Various materials have been researched with an eye to their use as electrode material for lithium ion batteries. Among the various materials, transition metal oxides, such as LiCoO2, LiNiO2 and LiMnO4, have attracted considerable attention as cathode material for a lithium secondary battery. However, the cathode material for the lithium secondary battery has problems in that environmental problems occur, manufacturing costs thereof are high, and thermal stability thereof decreases when it is in a charged state.
In order to solve the problems, LiFePO4 has been actively researched as an alternative to cathode materials for a secondary battery, such as transition metal oxides.
The LiFePO4 has many advantages in that thermal stability is excellent because (PO4)3− has a strong covalent bond, the discharge capacity thereof is high, and this discharge capacity only slightly reduced even after undergoing numerous charge and discharge cycles.
However, the LiFePO4 has disadvantages in that the electric conductivity thereof is low and the diffusion rate of lithium ions is low.
As a method for solving the problems, there is a method of improving the rate capability of electrode material by synthesizing an electrode material having small sized particles and a uniform particle distribution. Various methods of synthesizing LiFePO4 having nanostructured particles and a uniform particle distribution, such as a sol-gel method and a solid reaction method, are being researched.
However, a high-temperature post heat treatment process must be performed so as to synthesize LiFePO4 having high crystallinity using the conventional sol-gel method or solid reaction method. Accordingly, there are problems in that the process of synthesizing the LiFePO4 is complicated and the manufacturing cost thereof is increased. Furthermore, there are problems in that particles grow and electric conductivity is decreased.